Basically, the Red Cross was having a ceremony to honor the RC volunteers in Orange County. This group was supposed to sing, but the RC didn't like their choice of material as it might "offend" some people and the Red Cross (is claiming) to be a-political, and sectarian. The offensive tunes included America The Beautiful, Lee Greenwood's God Bless the USA, and another tune that was written for Columbine (A Student's Prayer, or something like that).
The letter that was sent included a sentence that read something like "... and the Declaration of Independence might be considered offensive by some." (I think they were listing things that could be considered offensive, like the use of religious or patriotic material.)
Anyway, it seems the Red Cross of Orange County believes the Declaration of Independence to be an offensive document.